The present invention relates generally to infrared polarimeters, and more particularly to an infrared laser polarimeter system for measuring polarization properties and electro-optic and magneto-optic constants of infrared transmissive materials.
Existing polarimeters are generally configured to use polarization information to measure single quantities which are not necessarily descriptive of material properties of a sample. A Mueller matrix photopolarimeter for making scattering ellipsometry measurements was described by Thompson et al ("Measurement of polarized light interactions via the Mueller matrix", Appl Opt 19, 1323-1332 (1980)). This instrument is complicated, requires four Pockel cell modulators and multiple lock-in amplifiers and, by the nature of the data acquisition process, has limited accuracy. Azzam (U.S. Pat. No. 4,681,450) described an instrument for measuring the Stokes vector and which is capable of measuring the Mueller matrix of a sample, but is limited to the visible spectrum because the design requires visible light detectors. No other known instruments are configured for measuring the Mueller matrix of materials in transmission.
The invention solves or substantially reduces in critical importance problems with prior art polarimeters by providing an infrared laser polarimeter for measuring polarization properties of infrared transmissive materials and fundamental electro-optic and magneto-optic constants of these materials. The invention measures the Mueller matrix to acquire a complete description of the polarization properties of the sample, and includes an infrared laser source, a series of rotatable infrared polarization elements and an infrared detector. The sample is placed between two sets of rotatable polarization elements which may comprise combinations of a linear polarizer and a linear retarder. The Product of the method and subsequent data reduction is a 4.times.4 Mueller matrix containing information about the polarization properties of the sample (e.g., retardance, diattenuation, depolarization, scattering) except absolute phase. The infrared laser Polarimeter of the invention provides polarization and material property information as does the infrared spectropolarimeter described previously, but the invention provides the information at specific selected wavelengths and with greater spectral resolution at those wavelengths than that provided by the infrared spectropolarimeter.
It is therefore a principal object of the invention to Provide an infrared laser Polarimeter system for measuring polarization properties of materials.
It is a further object of the invention to provide an infrared laser polarimeter system and method for measuring the fundamental electro-optic and magneto-optic constants of infrared transmissive materials.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.